Projecting the potential impacts of climate change on water resources for the Conterminous United States through high resolution hydro-meteorological simulation

This study describes an enhanced hydrologic modeling approach to assess the potential impacts of climate change on water availability for various hydrologic Subbasins (HUC8s) in the conterminous US. For this purpose, a macro scale hydrologic model, Variable Infiltration Capacity (VIC), was calibrated and validated at a refined 4-Km spatial resolution. The simulated VIC runoff, forced by 1980-2008 DAYMET meteorological observation and bias-corrected by PRISM (Parameter-elevation Regressions on Independent Slopes Model), was calibrated to USGS WaterWatch monthly runoff observations for 2017 HUC8s. The potential impacts of climate change on future water resources were assessed through 4-Km VIC model simulations driven by projections from an ensemble of multi-GCM driven integrations including downscaled and bias-corrected daily data from regional climate models (RegCM4 and WRF) for 40 years in the historic period (1966-2005) and 40 years in the near-term future period (2011-2050). Results from model calibration and validation in historic time period showed reasonable spatial and temporal predictability of monthly runoff for 2017 HUC8s in the conterminous US, suggesting that a multi-site calibration strategy is necessary to accurately predict spatial variation in watershed hydrology at Subbasin Hydrologic scale. Moreover, the spatially varying pattern of streamflow variability under future climate conditions also suggests that regionally specific management strategies are necessary to mitigate the potential impacts of climate change on water resources.